Facsimile signals representing graphic original material are generated by scanning the graphic original line by line to produce a rectangular array of generally parallel horizontal lines known as a raster familiar on television screens. Each line of the raster is a series of analog or digital pulses. The facsimile recorder which receives the facsimile signals prints them line by line on sensitive paper fed by a linear printing head.
Teletype signals represent alphanumeric characters of a predetermined configuration as compared to the random graphic elements of a facsimile weather map, for example, and are transmitted in a seven bit dot-dash code with a combination of five pulses for each character. Such coded on-off pulses would be recorded unintelligible if applied to a conventional facsimile recorder because they are not in raster form. It has been proposed that coded teletype signals be decoded for analog printing in computer systems, but prior systems have not been compatible with facsimile signal transmission.
Accordingly it is the object of the present invention to provide a facsimile system for recording with conventional facsimile signals and teletype signals and further to distinguish which of the two types of signals is received.